Interconnection in a network of electronic equipment is typically governed by standard data "protocols" which specify how a particular node in the network will receive and transmit information over the network. This information is generally contained in "packets" having a definite format and a packet is preceded and terminated by special symbols for ease of recognition.
Connection management procedures are designed to recognize these special symbols and to initiate proper connection to the network. The procedures should avoid false connection as well as detect the presence of spurious signals on the network. Generation of spurious signals on the network is obviously an important problem.
Spurious signals can arise from excessive noise on the network. In a typical network configuration, nodes on the network act as "repeaters". That is they receive signal packets, decode them, encode them and transmit them to another node. Spurious symbols received should, accordingly, be detected and not propagated. This detection process aids in the isolation of faulty nodes. Additionally, these noisy symbols could be misinterpreted as connection management symbols and could falsely initiate connection of a node to the network.
Besides noisy symbols, a portion of a packet may have a parity error which could also be misinterpreted.